http://stackoverflow.com/questions/29996909/share-immutable-reference-in-a-http-server

thread_local.rs

#![feature(scoped_tls)]
#[macro_use] extern crate nickel;

use nickel::Nickel;
use nickel::router::http_router::HttpRouter;
use nickel::ResponseFinalizer;

struct MyObject;

impl MyObject {
    fn foo(&self) {}
}

scoped_thread_local! (static MY_OBJECT: MyObject);

struct Middle;
impl nickel::Middleware for Middle {
    fn invoke<'a, 'b> (&'a self, _: &mut nickel::Request<'b, 'a, 'b>, res: nickel::Response<'a>) -> nickel::MiddlewareResult<'a> {
        MY_OBJECT.with (|obj| obj.foo());
        "hi\n".respond (res)
    }
}

fn serve(obj: &MyObject) {
    let mut server = Nickel::new();
    let mut router = Nickel::router();

    MY_OBJECT.set (obj, || {
        router.get("/foo", Middle);

        server.utilize(router);
        server.listen("127.0.0.1:6767");
    })
}

fn main() {
    let obj = MyObject;
    serve(&obj);
}

unsafe.rs

#[macro_use]
extern crate nickel;

use nickel::Nickel;
use nickel::router::http_router::HttpRouter;
use nickel::ResponseFinalizer;
use std::mem::transmute;

struct MyObject;

impl MyObject {
    fn foo(&self) {}
}

struct Middle (&'static MyObject);
impl nickel::Middleware for Middle {
    fn invoke<'a, 'b> (&'a self, _: &mut nickel::Request<'b, 'a, 'b>, res: nickel::Response<'a>) -> nickel::MiddlewareResult<'a> {
        self.0.foo();
        "hi\n".respond (res)
    }
}

fn serve(obj: &MyObject) {
    let mut server = Nickel::new();
    let mut router = Nickel::router();

    router.get("/foo", Middle (unsafe {transmute (obj)}));

    server.utilize(router);
    server.listen("127.0.0.1:6767");
}

fn main() {
    let obj = MyObject;
    serve(&obj);
}